Automatic cut-off device



June 24, 1958 M. HOFER 2,840,064

AUTOMATIC CUT-OFF DEVICE Filed Aug. 16. 1954 2 Sheets-Sheet 1 I N, Fig. 1. v

INVENTOR MAX HOFER BY MMMfW ATTOR N EYS June 24, 1958 M. HOFER 2,840,064

AUTOMATIC CUT-OFF DEVICE Filed Aug. 16. 1954 2 Sheets-Sheet 2 INVENTOR MAX HOFER ATTORNEYS excessive number of R. P. M.

United States Patent AUTOMATIC CUT-OFF DEVICE Max Hofer, Augsburg, Germany, assignor to Maschinenfabrik Augsburg-Nurnberg A. G., Augsburg, Germany, a corporation of Germany This invention relates to automatic cut-off devices and more particularly to such devices for automatically stopping internal combustion engines upon the occurrence of excessive speed or deficient lubricating oil pressure.

In the operation of internal combustion engines it may be desired to incorporate in'the engine controls a device or devices for automatically stopping the engine in cases of unsafe conditions of operation. Particularly it may be desired .to have such a cut-off device for stopping the engine'in the event that the engine turns up an excessive number of R. P. M. and/ or in the event that the lubricating oil pressure falls below safely operating levels. Since such unsafe operating conditions usually result from some abnormal condition or breakdown, it may be desired to have such cut-off devices completely automatic and yet of such simplified and foolproof construction as to be readily operable by the usual unskilled personnel without special training.

Furthermore, with a cut-off for stopping the engine when an excessive number of R. P.M. 'is developed, the

stopping action may advantageously be sudden or substantially instantaneous; whereas, with a-device for stopping the engine in the event of lowered oil pressure, the

cut-ofi may advantageously operate more slowly to give time, for example, for the operator to recognize the difficultyin oil pressure and have an opportunity to correct it, without actually bringing the engine to a complete stop.

According to this invention, such an automatic cut-off device is provided to operate on, for example,'a'fuel control throttle through a hydraulic. servomotor so that, upon -the engine exceeding a predetermined number of R; P. M.

and/or the lubricating oil pressure-dropping below a-predetermined level, the flow of hydraulic fluid to the servomotor is automatically interrupted causing the servomotor to close the fuel throttle and cutoff further supply fuel to the engine. Furthermore, the device. according to this invention provides for a sudden or substantially instan- -.taneous closing of the throttle upon an excessively high number-of R. P. M. and a more .gradual closing of the throttle upon dropping of the lubricating oil pressure below .the predetermined level.

It is, accordingly a principalobject of this invention to provide a cut-off device of the character described for interrupting, through a servomotor, fuel feed to an internal combustion engine upondropping of the lubricating oil pressure therein and/ or upon the occurrence of an A further-object of this invention is to providein acut-off device of thecharacter describeda governing member responsive to the engine speed for stopping the engine through a hydraulic wservomotor when .a predetermined number of R.:P. M. is reached Y Another, bjectof-this invention is to provide inia cut-01f device of the character described automatic means responsive tothe lubricating oil pressure in the engine for stopping the enginethrough'a hydraulic servomotor when a predetermined low lubricatinglp'il. pressure is reached j: a .w

'conduit 6 through an oil free Still another object of this invention is to provide a combined automatic cut-off device of the character described having independently acting speed-responsive and oil-pressure-responsive devices for automatically cutting off fuel feed to the engine through a hydraulically actuated servomotor control when either an excessivespeed condition or a deficient oil pressure condition obtains during the engine operation.

Still another object of this invention is to provide in such an automatic cut-off device means for resetting the device after actuation thereof. 7 g

A still further object of this invention is to provide in such an automatic cut-ofl device a substantially instantaneous speed-responsive member for eflecting sudden or substantially instantaneous actuation of a feed control servomotor.

Still another object of this invention is to provide in such "an automatic cut-off device an oil-pressure-responsive member effective for gradually actuating a fuel control servomotor.

QA still further object of this invention is to provide an automatic cut-ofl device of the character described of simple and economic construction and dependable automatic operation yet without electrical or mechanical complexity as would require greater skill or training than normally obtains with operators of the engine to which 'it is applied. 7 I

Other objects and advantages will be apparent from the following description, the attached drawings and the appended claims.

In the drawing, p

v Fig; 1 is a vertical section through a fuel'con'trol servo motorof an engine embodying this invention;

3 Fig; 2 is a plan view of the speed-responsive and oilpressure-responsive'cut-ofi means;

Fig. 3 is a section along the lines III-III of Fig. 2; Fig. 4 is a section along the lines IV-IV of Fig. 3; and

Fig. 5 is a vertical section through the device of Fig. 2.

Referring to the drawings,-in which like reference numerals denote like parts throughout the several views, Fig. 1 indicates a' hydraulically actuated fuel control servomotor for controllingfuel feed to an internal cornbustion engine having the invention applied thereto. The

servomotor comprises a power piston 2 connected through a lever 1 to an engine speed regulator (not shown) and to a slide valve 3 which controls the admission of hydraulic fluid to operate the piston 2.- The hollow piston shaft 2a surrounds the slide valve 3 and is connected through a' linkage 4 to the regulating rods or fuel feed throttle for the engine. A spring 5 urges piston 2 and slide -valve. 3 downwardly in the drawing against the action of hydraulic fluid supplied beneath piston 2 from :filter'7, as 'indicated by the arrows in Fig. 1. a a 1 Thus, hydraulic fluid under pressure working against thefbottom 'of piston 2 tends to raise'thepiston against the action of spring Sand tomovelthe'fuel feed throttle into open position through the linkage4; whereasra stoppage ordecrease in pressure of the hydraulic-fluid supplied beneathpiston 2 allows the spring 5 to forcethe piston downwardly in Fig. 1. and movefithe feed fuel throttleto closed position through the linkageA;

In the operationfof theautomatic'cut-oif device, how- .ever, the rapidity orsuddenness with which piston 2"and the: linkage 4 is tmovedto closed? position depends 'on,

.ahrongotherthings, the.rapiditywithwhich the hydraulic -fluid;can;be discharged from, beneath piston. 2. ..Acco-rdringly, :for rapid operation'of .the "cut-off device, asiin the case where :the engine'is attaining an excessively. high speed,l'a large discharge area for. the hydraulic pressure ..b.eneath' piston-1'2 (is preferred. 'For more: gradualwoperabothlpistons being mounted in-series in the line of flow of hydraulic fluid toward the servomlotorthrough conduit 6.

Referringin detail to Fig. 5, the automatic excessive speed cut-off includes a quick acting speed-responsive device 8 and a control piston 13 mounted in a housing. The speed-responsivemember comprises an eccentric ring mounted around a shaft 33 which revolves with the en- :gine crankshaft (not shown), Eccentric ring 10 is maintained-concentrically about theaxis'of shaft 33 under the action of a spring 9. During rotation of shaft 33 centrifugal force tends to urge the heavy side of eccentric =ring'l0'radially outwardly from shaft 33 against the action of spring 9. Thus, the out-of-balance weight of eccentric :ring 10 is correlated with the strength of counteracting spring -9 so that, uponattaining a predetermined number wardly from :the axis of shaft 33 sufficiently to'engage pin 11 and, by meansof pin 11, to release pawl 12j-piv- :oted in control piston 13.

Thus, during normal operation of the engineat speeds less than the predetermined number of R. -P. M. above which pawl 12 will be disengaged as above noted, pawl .12 engages stop 34in housing '14 and holds piston 13 toward the rightin Fig, 5 in such position that ihydraulic fluid tfor a'ctuating'ripiston 2 of the-servomotor has free passage from the supply of fluid ;under pressure (not shown) into housing '14 at through passages and 23, 'aroundpiston .13 via -a circumferential valve groove 17 therein, and out of housing 14 via passage 37 which com- .municates'directly to conduit 6 leading the hydraulic'fluid to the servomotor. That is,-as lo'ngas pawl 12 remains engaged (against stop 34 in :housing 14 maintaining the ipiston 13:t'o the right in the drawingasshown-in Fig.5, hydraulic cfiuid has free passage through piston :13 and "conduit-6m the'servom'otor tt'o maintainpist'on 2 thereof in raised position Sand the "fuel throttle open. -When, on the other hand, shaft 33 exceeds' thepredetermined number of R.--P. M.,the1out-of-balance weight ofeccentric vring 10"willoverc'ome the force'of spring 9, move radially =outwardfrom the "axis of 33,' 'strike pin 11 and disengage :pawl 12 from stop 34. Upon such disengagementof pawl "12, piston 13 is forced'to the left in thedrawing 'by'the ac'tion'of spring 15 thereby movingthe valve groove 17 "out of alignment with passages 23 and 37 and interrupt- .ing the flow of hydrauliefluidtherethrough to conduit'6 and the servomotor. a

In addition, inthe'furthes't left 'position of piston 13', as indicated in Fig.3, the valve .:groove :17'moves into align- "ment withpassage 16, communicating with conduit 6, and r a passage indicated at 38 leading to the hydraulic fluid r'es'ervoir. Thus, in the furthest left position of the piston 1'3,notonly is'the passageof further hydraulic fluid into conduit 6 interrupted, but the free hack flow of hydraulic fluid outof conduit 6 through passages16 and is assured; thereby almost instantaneously relieving substantially all the pressure beneathipiston 2 in "th'eservomotor and permitting spring 5 to 'move :piston 2 rapidly dow n- "wardly to close 'the ifuel' tlir'ottle' almostinstantaneously.

Thus, "in the case where :the engine may exceed the Jpjr'edetermined number "of rrvolutionsfor which the speed responsive member 8 'is set, disengagement of pawl 12 tand movementsof piston 13 to'thefleft in=the drawing not cihskofi further admission .of hydraulic fluid to 'tlie 4 piston 2 of the servomotor but also provides for rapid and substantially instantaneous discharge of hydraulic fluid from under piston 2fto effect virtually immediate closing of the fuel throttle linkage 4 by the spring 5 of the servomotor.

In order to reset the speed-responsive cut-off device for continued operation, a pull knob arrangement 18 is provided on piston 13 whereby the piston can be manually moved to the right against'the action of spring 15 until pawl 12 once again engages stop 34 and maintains the piston 13 in the right-hand position until the eccentric ring 10 again dislodges'the pawl 12 through pin 11. In this right-hand position, as above noted, the hydraulic "fluid for the servomotor has free access to conduit 6 thereof through passages 23, 37-and valve groove 17.

Illustrative of the oil-pressure-responsive cut-off device of this embodiment, a control piston 19 is also mounted in housing 14 for 'free lateral'movement therein. A sampling line '20 supplies against the left end of piston 19 oil pressure taken from 'the engine bearing lubrication system. During normal operation of the engine, this oil pressure acts against the left end of piston 19 urging it to piston 2 of the servomotor.

Since a sudden orinstantaneous cut-otfof the'engine fuelfeed maynot be desired with a drop in lubricating ollpressure, it is not-necessary with the actuation of the oil-pressure-responsive device to have the rapid discharge of hydraulic fluid from beneath the servomotor piston 2 as was describedin connection with the speed-responsive cut-off, piston '13. Accordingly, a bleed-off groove 32, of substantially less capacity than conduit 6, is provided adjacent piston 2 in the servomotor so that, with the closing by piston 19 (i. e., moving to the left in Fig. 5') of the passages 36, 35, 23, and 37 to conduit 6, the

hydraulic fluid under piston 2' is gradually bled off through :groove 32 as spring 5 gradually forces piston '2 and slide valve 3 downwardly in 'Fig. '1 to close the fuel throttlelinkage t gradually. I

In order to set the oil-pressure-responsive piston 19 to operative position, apull knob and shaft 24 is mountedinpiston '19. The piston is manually moved to the -r1ght 1n the drawing sufficiently for the two arresting pins 25 to snap into appropriate notches 26 on the 'pull knob shaft 24. In this-position, the valve groove 22 in piston 19 is at'least-partially alignedwith passages 35, 23, etc.,

to provide passage of hydraulic fluid from 36 through the control device to conduit 6 leading to servomotor. As 'theengine runs and lubricating oil pressure builds up the sampling line 20, .piston 19 is moved still further to the right under the effect of increasing oil pressure acting against spring 21 until such time as the arresting pins -25 are pressed radially outwardly out of engagement with the notches 26 by the action of shell27 mounted in piston 19 around shaft 24.

Upon release of the arresting pins 25, pull knob shaft 24 (but not piston 19) is forced to the left withinpiston 19 by the action of-spring 28 so that the notches 26 are to the left of and out of engagement with arresting :pins 25. Thus, piston 19 is free to move throughoutits extent of lateral displacement under the counteracting forces of the lubricating oil pressure admitted into housing 14 by the sampling line 20 and the' action of spring 21. g l i Housing -14 also includes a discharge groove 29 through which oil may be constantly bled on to achieve freer movement of-piston19inresponseto the opposed forces of the oil pressure admitted at 20 and the spring- 21; To

a the extent that the force of spring 21, correlated with the minimumoil pressure desired, overbalances the oil pressure delivered to piston 19, piston 19 is moved to the left, with accumulated oil being bled ofi over the groove 30, through the passage 31. I

It will thus be noted that an automatic cut-off device is developed according to this invention providing for a sudden or virtually instantaneous cut-off of engine fuel feed when an excessive speed occurs and, also, a more gradual reduction in fuel feed upon the dropping of lubricating oil pressure below a predetermined value. The device, afteroperation, may be manually set or reset quite simply, and does not require a skilled operator as with electrical and other automatic cut-off devices yet is positive, automatic and dependable of operation whenever the engine is running. Also, although the speedresponsive and oil-pressure-responsive cut-off members are described as being sequentially mounted and operated in the hydraulic fluid supply line to the servomotor, the two devices act independently of each other to the extent that each will function to stop the engine upon the happening of the particular abnormal operating condition for which it is designed. As will be understood, either device singly could be incorporated separately in an engine embodying this invention notwithstanding that, when arranged, in sequential or interdependent manner as illustrated, the operation. of either device precludes or affects operation of the other.

While the forms of apparatus hereing described constitute preferred embodiments of the invention, it isto be understood that the invention is not limited to these precise forms of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

1. In an automatic cutoff device of the character described for stopping an internal combustion engine at a predetermined number of R. P. M. and a predetermined minimum lubricating oil pressure which comprises in combination a hydraulically actuated servomotor for controlling fuel feed to said engine in accordance with the supply of hydraulic fluid to said servomotor, means responsive to the speed of said engine for interrupting said supply of said hydraulic fluid to said servomotor at said predetermined number of R. P. M., discharge means for rapidly withdrawing from said servomotor upon the operation of said speed responsive means hydraulic fluid supplied to said servomotor eifecting rapid interruption of fuel feed to said engine, oil pressure responsive means for interrupting said supply of hydraulic fluid to said servomotor at said predetermined lubricating oil pressure, and means for bleeding off from said servomotor hydraulic fluid supplied thereto, said means for bleeding off having substantially less capacity than said means for withdrawing hydraulic fluid effecting more gradual operation of said servomotor in response to said oil pressure responsive means than in response to said speed responsive means.

2. In a self-actuating cutoff device for automatically stopping an internal combustion engine having a hydraulically actuated servomotor control for the fuel feed thereof, the combination which comprises a spring loaded slide valve for interrupting flow of hydraulic fluid to said servomotor, releasable locking means for maintaining said slide valve in open position against said spring loading, means responsive to the speed of said engine for automatically releasing said releasable locking means at a predetermined number of R. P. M., rapid discharge means for suddenly withdrawing said hydraulic fluid from said servomotor in the closed position of said slide valve, piston valve means responsive to the lubricating oil pressure in said engine for interrupting said supply of hydraulic fluid to said servomotor and said slide valve at a predetermined lubricating oil pres sure, and bleed-oif means for relieving the hydraulic 6 pressure in said servomotor in the closed position of said piston valve.

3. In a self-actuating cutoff device for automatically stopping an internal combustion engine having a hydraulically actuated servomotor control for the fuel feed thereof, the combination which comprises a spring loaded slide valve for interrupting flow of hydraulic fluid to said servomotor, releasable locking means for maintaining said slide valve in open position against said spring loading, means responsive to the speed of said engine for automatically releasing said releasable locking means at a predetermined number of R. P. M., rapid discharge means for suddenly withdrawing said hydraulic fluid from said servomotor in the closed position of said slide valve, piston valve means responsive to the lubricating oil pressure in said engine for interrupting said supply of hydraulic fluid to said'servomotor at a predetermined lubricating oil pressure, and bleed-oif means for relieving the hydraulic pressure in said servomotor in the closed position of said piston valve, said bleed-off means having substantially less capacity than said rapid discharge means.

4. In a self-actuating cutoff device for automatically stopping an internal combustion engine having a hydraulically actuated servomotor cont-r01 for the fuel feed thereof, the combination which comprises piston valve means responsive to the lubricating oil pressure in said engine for interrupting 'said supply of hydraulic fluid to said servomotor at a predetermined lubricating oil pressure, spring means urging said piston valve against said oilpressure, bleed-01f means for relieving the hydraulic pressure in said servomotor in the closed position of said piston valve, releasable locking means vfor holding said piston valve into open position before operating oil pressure is reached during start-up of said engine, and means for automatically releasing said locking means when said operating oil pressure is reached in said engine.

5. In an automatic cutotf device of the character described for stopping an internal combustion engine at a predetermined number of R. P. M. and a predetermined minimum lubricating oil pressure which comprises in combination a hydraulically actuated servomotor for controlling fuel feed to said engine in accordance with the supply of hydraulic fluid to said servomotor, means for interrupting said fuel feed when the supply of said hydraulic fluid to said servomotor is interrupted, means responsive to the speed of said engine for interrupting said supply of said hydraulic fluid .to said servomotor at said predetermined number of R. P. M., discharge means for rapidly withdrawing from said servomotor upon the operation of said speed responsive means hydraulic fluid supplied to said servomotor, oil pressure responsive means for interrupting said supply of hydraulic fluid to said servomotor at said predetermined lubricating oil pressure, means-for bleeding off from said servomotor hydraulic fluid supplied thereto, said means for bleeding 01f having substantially less capacity than said means for withdrawing hydraulic fluid effecting more gradual operation of said servomotor in response to said oil pressure responsive means than in response to said speed responsive means, and resetting means for releasably maintaining said speed responsive and oil pressure responsive means in open operating position.

6. In an internal combustion engine having a hydraulically actuated servomotor for continuously regulating and controlling fuel feed to the said engine, an automatic cutoif device for stopping said engine at a predetermined number of R. P. M. and a predetermined minimum lubricating oil pressure which comprises in combination means for supplying hydraulic fluid to said servomotor for the continued operation thereof to control said fuel feed to 7 said engine, means responsive to the speed of said engine and interposed in said hydraulic fluid supply means for interrupting supply of hydraulic fluid to said servomotor at said predetermined number of R. P. M., discharge means for rapidly withdrawing hydraulic fluid from said *servomotor upon operation of said speed responsive means effecting substantially immediate action by said s'erv'omotor -to interrupt fuel feed to said engine and oilflpre'ssure responsive means interposed in saidhydraulic fluid supply means for interrupting jsaid supply of 'hydraulicfluid to said servomotor at-said predetermined minimum lubricating oilpressure effectinggradual operation of sa'id s'ervomotortoreduce fuel feed to saidengine. 7. A safety cutoff device of'rthe character described for an internal; combustion engine having a hydraulically actuated servomotor for automatically regulating fuel feed to said engine comprising incombination means for supplying hydraulic'fluid'to said servomotor, -first cutoff means interposed in said hydraulic fluid supply'means and resp'onsiveto'the speed of said engine for interrupting supply of hydraulic 'fluid to said servomotor at a predetermined maximum engine speed and independentlyof the normal auto'maticoperationof said servomotor, rapid dischargerheans for rapidlywithdrawing from'said servomotor upon operation of said first cutoff means hydraulic fluid suppliedmthereto effecting substantially immediate actuation thereof to interrupt fuel feed, to said engine,

second cutoff means interposed: in said hydraulic fluid supply 'means and responsive to lubricating oil pressure in said engine for interrupting supply .ofhydraulic 'fluid to said :servomotor at a predeterminedminirnum lubrieating oil pressure and independently of thenormal auto- -rnaticoperation of said servomotor, and slow discharge means 'for bleeding off upon-operation of vsaid second cutoff means fluid suppliedto said servomotor at a rate I substantially less than said irapid discharge means effecting gradual operation of said servomotor to reduce fuel feed to saidengine. a

8. -lnan internal combustion engine having a hydraulically actuated servomotor for automatically and continuously regulating fuel feed to said engine during normal operation thereof, a safety cutoff deviceindependent of said automatic regulation by said servomotor which comprisesin combination cutoff means for interrupting "further supply of hydraulic fluid to said servomotor effecting interruption of said automatic regulation of said fuel 'feed by said servomotor, means responsive to the lubricating oil pressure in said engine effecting operation of said cutoff device at a predetermined minimum lubricating oil pressure, releasable means for maintaining said cutoff means in inoperativeposition prior to starting said engine, andLbIeed-Off means for gradually withdrawing from said 'servomotor hydraulic fluid supplied thereto prior'to operation ofsaid cutoff means effecting gradual operation of said servomotor'to reduce fuel feed to said engine'after lubricating oil pressure thereof falls below said predetermined minimum pressure.

'R eferences Cited in 'the file of'thispatent UNITED STATES PATENTS 

